Technical Specification Releases 8 to 11 of the Third Generation Partnership Project (3GPP) for standardization of mobile technologies adapt horizontal beam forming using multiple antenna ports provided in a lateral direction at a base station.
In 3GPP Release 12, 3D-MIMO for achieving vertical beam forming, in addition to the horizontal beam forming, has been discussed. See, for example, Non-patent Documents 1 and 2 listed below. By forming a beam in a vertical (or elevation) direction and a horizontal (or azimuth) direction, system characteristics are expected to be improved.
In 3GPP standardization, 3D-MIMO scheme using eight or less transmission antenna ports is called “elevation beamforming” and 3D-MIMO with antenna ports greater than eight is called full-dimensional (FD) MIMO. Apart from the standardization, FD-MIMO is named a massive-MIMO and the antenna layout is not limited to two-dimensional or three-dimensional layout.
FD-MIMO is a technique capable of greatly improving the efficiency of frequency use by using a large number of antenna ports or antenna elements at a base station to form a sharp (directional) beam. By providing a number of antenna ports to a base station, beam forming in horizontal and vertical directions is achieved, just like elevation beamforming.